The invention relates to a leno device.
Leno devices are used for the production of leno fabric. A leno fabric is a fabric in which at least two warp threads do not run parallel to each other, but loop around each other. For example, a warp thread moves as the standing thread straight through the fabric, while another warp thread is moved as a loop thread zigzagging over or under the standing thread and, alternately, forms—on the one or the other side, a downward or upward directed loop for receiving the weft thread. In order to illustrate this, FIG. 8 shows, schematically, a detail of a leno fabric with standing threads S1, S2, S3, S4, loop threads S5, S6, S7, S8, and warp threads K1, K2, K3. Illustrated here is a simple structure that can be designed so as to be complex as desired.
In order to produce such fabrics, the mentioned leno devices are used, these being shown, e.g., by document CH 391595. The leno device is also referred to as a “doup warp heald frame” and is divided into two lifting shafts and one half shaft. While the lifting shafts of a dobby are driven by, e.g., a rod assembly, so as to move up and down in vertical direction, the half shaft is moved by a spring-biased yoke which is alternately carried (in downward direction) by one or the other pull shaft. Such a system certainly works, however, the operating speed must remain restricted. In fact, weaving machines with such leno devices are operated in the range of 150 to a maximum of 250 wefts per minute. Due to the low productivity achieved in this manner, the produced fabrics become extremely expensive and, consequently, their use remains greatly restricted.
It is the object of the present invention to provide an apparatus for driving the half shaft, said apparatus permitting the production of leno fabrics by means of lifting healds and half healds at a substantially higher weft speed. In particular, the apparatus should be simple and robust.